OK to mount arrays on rack raised above RV roof?

cibi
cibi Registered Users Posts: 3 ✭
in Solar Beginners Corner #1
I'm reluctant to put holes (and weight) on the aluminum roof of my horse trailer/RV so prefer to mount solar panels on the factory-installed roof-mounted hay rack. Is this a good plan, or would having the arrays "ventilated" on their underside somehow compromise the system?  Thanks from a complete solar novice. 
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,662 admin
    #2
    Solar panels will work slightly better if ventilated (cooler cells run slightly higher Vmp working voltage).

    Mostly--Just need to make sure that they are mounted solidly to the structure so they do not get blown away while traveling.

    Note--Solar panels are relatively thin tempered glass. The panels cannot be "torqued" or they will shatter (where you are mounting the panels, the mounting frame/trailer roof must be rigid).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    #3
    I would worry a bit that your factory mounted hay rack is not engineered to take the type of uplifting forces that solar panels, at highway speed, will produce.  

    On residential roof mounted systems, it is considered best practice to have at least 4 inches (6 is better) of airspace below the panels for ventilation.   On an RV, the space is often omitted because it increases the force on the mounts. 

    If one of those panels flies off your trailer, after the lawyers are done you won't be able to afford horses or trailers.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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  • cibi
    cibi Registered Users Posts: 3 ✭
    #4
    Can afford neither horses (thus conversion of trailer from h's to camper) nor stupid mistakes, which is why I asked the question.  Will have to rethink how to mount the panels.
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  • scrubjaysnest
    scrubjaysnest Solar Expert Posts: 175 ✭✭✭
    #5
    In the RV world, panels are typically mounted about 1 1/2 inch to 2 inches above the roof line. Many are using 3M VHB tape to attach the Z brackets. to avoid putting holes in the roof. Some RV manufacturers are using the same attachment system. I have not heard of any solar panels becoming missiles on the highway except for one mounted to an A/C plastic shroud. I used 3M VHB 4910 with 3M 5200 caulk/adhesive. Because mine tilt I did use 2 pop rivets in each bracket to the aluminum roof skin. Might give you some other options.
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  • Xizang
    Xizang Registered Users Posts: 50 ✭✭
    #6
    On panels facing hurricane force winds just going down the highway, would long aluminum stringers running lengthwise with the trailer, fastened to the ribs or bulkheads, give ample attachment?  Attaching the panels to those stringers would offer maximum attachment and also allow airflow under and above the panels, right?
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  • cibi
    cibi Registered Users Posts: 3 ✭
    #7
    Thanks all for the information and advice.  
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  • K4KMG
    K4KMG Solar Expert Posts: 50 ✭✭
    #8
    Max height on US roads is 13.5 feet.
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  • Shadowcatcher
    Shadowcatcher Solar Expert Posts: 228 ✭✭✭
    #9
    We have ABS plastic mounts for our 185W high voltage panel. I did not want to put holes in our Filon roof so I had a long talk with a 3M VHB engineer who gave me an Idea of how much contact area I would need for the wind load. It is still on and there have been loads in excess of 150MPH. If I were to do it another way I would be using 2 or 3" wide aluminum angel, drilled and tapped into the side of the panels.  
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  • grizzzman
    grizzzman Registered Users Posts: 18 ✭✭
    #10
    The solar panels on my MH are 6" off the roof. I would be VERY surprised if the hay rack wouldn't hold just fine. (A bale of hay has a MUCH larger wind drag then a panel)
    Boondocking is my game
    640 Watts Mono Bogart TM2030 and SC2030  Controller GC 6V 208 AH  Costco batteries  300 Watt Inverter and 2000 watt inverter 100AH LIFEPO4 2P4S
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  • Saburai
    Saburai Solar Expert Posts: 32 ✭✭
    #11
    grizzzman said:
    The solar panels on my MH are 6" off the roof. I would be VERY surprised if the hay rack wouldn't hold just fine. (A bale of hay has a MUCH larger wind drag then a panel)
    I'd tend to agree. However, if we are thinking in terms of potential aerodynamic lift, then maybe not so much?
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  • grizzzman
    grizzzman Registered Users Posts: 18 ✭✭
    #12
    One panel is inline with the MH and one is 90° and kiddy corner from each other. There are 4 mounts per panel of two 5" pieces of 3/16 T6 aluminum angle iron, 3 screw's and dicor. The first trip was 80mph with a 40mph cross wind. It has seen the rev limiter (90mph) personally I believe you are concerned over nothing. My father used silicone and just glued his panel on ( I have to admit that's a bit spookie for me)
    Boondocking is my game
    640 Watts Mono Bogart TM2030 and SC2030  Controller GC 6V 208 AH  Costco batteries  300 Watt Inverter and 2000 watt inverter 100AH LIFEPO4 2P4S
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